Camera model) Intrinsic parameters I extrinsic parameters I projection Worksheet 2.1 F=5mm ·Z=1 meter a tree is 2 meters high, 0.5 meters wide What is the size of the tree appears in the image? Sketch the diagram Answer Ch2. Cameras v0.b2 16
Camera model | Intrinsic parameters | extrinsic parameters | projection Worksheet 2.1 • F=5mm • Z=1 meter • A tree is 2 meters high,0.5 meters wide. What is the size of the tree appears in the image? • Sketch the diagram. • Answer:___________ Ch2. Cameras v.0.b2 16
Camera model) Intrinsic parameters I extrinsic parameters I projection Picture element(Pixel) based image [x y]' is in meters, [] is transposition in matrix Lu, v in pixels which is easy to be measured by the camera Each pixel is Sx wide and Sy high Typically Sx= Sy =5. 46um(1um=1x10A-6m=1 micron) 1 pixel Sx=5. 46um Image= 1024X768 Sy=5. 46um pIXies CCD Charge-coupled device Ch2. Cameras v0.b2 17 Sensorhttp://en.wikipediaorg/wiki/charge-coupled_devicE
Camera model | Intrinsic parameters | extrinsic parameters | projection Picture element (Pixel) based image • [x,y]T is in meters, []T is transposition in matrix • [u,v]T in pixels which is easy to be measured by the camera • Each pixel is Sx wide and Sy high • Typically Sx = Sy =5.46um (1um=1x10^-6m=1 micron) Sy=5.46um Sx =5.46um Image= 1024x768 pixles 1 pixel CCD Charge-coupled device Sensor: http://en.wikipedia.org/wiki/Charge-coupled_device Ch2. Cameras v.0.b2 17
Camera model) Intrinsic parameters I extrinsic parameters I projection Worksheet 2.2 For an image of 1280x 1024 Sx= Sy =5.um What is the size of the image(CmoS or ccD senso Find the pixel size of your favorite camera. mage · Answer (CMOS sensor Hint: Key specifications. Array Element(SXGA 1280X1024 www.ovt.com (VGA) 640x480 oVT Camera chi ov9620/9120 Pixel Size 5.2um x 5.2um webcam camera Image Area 6.66mm x 5. 32mm Lens size Output 10-bit Digital RGB Raw Data Ch2. Cameras v0.b2 18
Camera model | Intrinsic parameters | extrinsic parameters | projection Worksheet 2.2 • For an image of 1280x1024 Sx = Sy =5.2um. • What is the size of the image (CMOS or CCD sensor)? • Find the pixel size of your favorite camera. • Answer:________________ Image (CMOS sensor) www.ovt.com OVT CameraChip OV9620/9120 webcam camera chip Hint: Ch2. Cameras v.0.b2 18
Camera model) Intrinsic parameters I extrinsic parameters I projection Image center In picture files, usually no negative pixel is used because the origin is at one of the corners e. g. the right bottom (1, 1)) Center of ccd is placed at c=(O, Oy) v(pixels) 768 512, 384)in pixels X CCD u(pixels 1024 Ch2. Cameras v0.b2 19
Camera model | Intrinsic parameters | extrinsic parameters | projection Image center • In picture files, usually no negative pixel is used because the origin is at one of the corners (e.g. the right bottom (1,1)) • Center of CCD is placed at C= (Ox,Oy) CCD u (pixels) v (pixels) (Ox ,Oy )= (512,384) in pixels x 1024 1,1 768 Ch2. Cameras v.0.b2 19
Camera model) Intrinsic parameters I extrinsic parameters I projection CCD Pixel u, v) based perspective Projection (onO,) in pixels is the image center Equ.(1), (2) is divided by sxi sv, resp Reca∥x=F*X/2-(1) y=F*Yc/Z-( U=(E/5x *(X Z0+Ox--- 3), F is in meter, F/Sx is in pixels °V=(F人5)*Yzd+oy--14,5/ Sx is in pixels U=x/s,+Ox, v=y/s,o,in pixels) A Point in 3D space is / XoYZ in meters(or pixels, still ok, because X zc and yzc are ratios The 2D image point is [u, v'in pixels Ch2. Cameras v0.b2
Camera model | Intrinsic parameters | extrinsic parameters | projection CCD Pixel (u,v) based Perspective Projection • (ox ,oy ) in pixels is the image center • Equ. (1), (2) is divided by sx ,sy, resp. • Recall x=F*Xc /Zc ---(1) • y=F*Yc /Zc ---(2) • u=(F/sx )*(Xc /Zc ) + ox -------(3),F is in meter, F/Sx is in pixels • v=(F/sy )*(Yc /Zc ) + oy -------(4), F/Sx is in pixels • u=x/sx + ox , v=y/ sx+ oy (in pixels) • A Point in 3D space is [Xc ,Yc ,Zc ] T in meters (or pixels , still ok, because Xc /Zc and Yc /Zc are ratios. • The 2D image point is [u,v] T in pixels Ch2. Cameras v.0.b2 20